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Friday, July 1, 2005

Gadget Bag: PowerHungry

Today's batteries help satisfy our insatiable


PowerHungryI'm power-hungry, although not in the way you might think. If your photo backpack is loaded up anything like mine, you have a lot of gear that requires batteries. Cameras, flashes, a light meter, a GPS receiver and a laptop computer make me more effective when I'm out shooting, but each piece of equipment requires power—lots of it. So when it comes to choosing the right battery to power all of those electronic gadgets, it's important to understand our choices, especially when they impact our ability to create photographs.

In the past, there wasn't much thought needed when considering batteries, as the high-performance choices were between alkalines and NiCd (nickel cadmium) rechargeables. Today's electronics, especially digital cameras, demand greater power and better performance, and Li-Ions (lithium-ions) and NiMH (nickel metal hydride) deliver on both counts.

Offering one of the strongest alternatives to NiCd and alkaline batteries, NiMH batteries store up to 40 percent more energy than NiCds and are more resistant to cold, providing reliable performance under chilly conditions. Unlike NiCds, which suffer a memory effect that steadily degrades the batteries' ability to hold a maximum charge when they're not fully discharged, NiMH batteries can be freely recharged at anytime. With the ability to be recharged approximately 500 times, they offer a cost-effective alternative to alkalines.

A AA-sized NiMH battery is rated for power in milliamps (mAh). Although early AA cells delivered about 800 mAh, current batteries offer power as high as 2500 mAh. If you currently own sets of the lower-power NiMH batteries, we'd recommend investing in a set with a minimum rating of 2100 mAh. This will allow high-draw devices such as a digital camera to last longer before the batteries require replacement.

One of the devices in which you'll see a big performance difference is flash. NiMHs deliver faster recycling times than alkalines, and performance doesn't decrease as the battery is depleted. The gain of just a couple of seconds can be important, especially when the flash is firing at full power.

Lithium-ion (Li-Ion) batteries are another option for photographers. They provide great capacity while being smaller and lighter than other batteries holding the same amount of energy. Like NiMH, they don't suffer from the memory problems, but Li-ions trump them by featuring better cold resistance and the ability to be recharged up to 1,000 times.

If you're using a digital camera that comes supplied with a rechargeable battery, it's likely a Li-Ion. Rather than being a AA-sized cell, however, these batteries often come in various shapes and sizes, requiring their own custom charger. If you want a backup battery, you'll need to invest in a second battery from the camera maker or one made by an independent battery manufacturer.

Disposable Lithium
Disposable lithium batteries outperform most other batteries. While they cost a little more than twice the price of many disposable batteries, they last three to five times longer than alkalines in digital cameras and electronic flash units. Like rechargeable batteries, lithiums deliver fast flash recycling and offer consistent power, even under cooler temperatures. Lithium disposables also have double the shelf life of alkalines; they're ideal as backups to rechargeable batteries.

Alkalines haven't gone the way of the dinosaur, despite the presence of higher-performance batteries, and for good reason. Not all devices demand high power, and for electronics such as a GPS receiver, radio or light meter, these batteries deliver stellar results.

Their biggest advantages are availability and price. You can purchase AA alkalines virtually anywhere, usually at a very affordable price. If you're desperately searching for batteries at a bazaar in Istanbul, Turkey, however, you'll likely pay a hefty premium.

Maintaining Power
Although Li-Ions and NiMHs have eliminated the memory problems of NiCDs, you still should take some basic steps to ensure that the batteries last longer and deliver at maximum capacity.

The first step is to prevent them from becoming deeply discharged—exhausted to the point where internal damage occurs. While we can be tempted to draw every volt of power out of batteries, it's better to make sure the battery charge level doesn't drop too far, especially when they're being stored. It's a good idea to top off your batteries once a month, whether you're planning to use them or not.

When the batteries are being used in high-draw devices, especially digital cameras, there's little warning about impending battery exhaustion. NiMH, Li-Ion and lithium batteries maintain a fairly constant voltage until they're nearly depleted. Since battery-check indicators rely on output voltage to estimate the battery's remaining strength, the camera isn't much better than you in predicting how many more shots you can expect from the battery. At best, they can report that you're "nearly" exhausted just before the camera quits. This is the best time to replace the battery with a fresh set.

All rechargeable batteries will lose a bit of their charge when they're just sitting in your camera bag. NiMH batteries tend to lose approximately one to two percent of their charge per day, so you could be in for an unpleasant surprise if you installed batteries in your gear that were charged weeks before. Take it from someone who has made that mistake, it pays to fully recharge all your batteries right before an important shoot.



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